The present invention relates to apparatus used in telecommunications, in particular to modularised network cards which are coupled to backplanes; and more particularly to a card having increased functionality.
Worldwide today, substantial demands are being placed on modern telecommunication networks by the increase in the numbers of telephone lines, pages, fax machines and subscribers to other data systems, such as the Internet. This increased demand is placing ever increasing pressure on telecommunication service operators to achieve greater throughput whilst achieving the so-called “five nines” operational availability (i.e., 99.999% up time) as well as provide the capability to support future functionality or features whilst keeping costs to a minimum. In telecommunication networks, service operators employ exchange rooms which have high-densities of high-power networking and processing equipment, which are all housed in a mechanical chassis. Many challenging considerations arise from having such a tightly packed arrangement of high-power equipment, including the need for specialist cooling systems, cabling arrangements and ease of maintenance. The “five nines” operational availability and other service level agreements (SLA's) impose great demands on network maintenance and the so-called “hot-swap” technology employed in equipment housed in a chassis allows faulty cards to be easily replaced.
Typically the mechanical chassis houses the electronic equipment which carries out networking and processing of routed data signals. The data signals may be transmitted on either electrical cables or optical fibre cables, which are often arranged around and supported by the outside of the chassis. The cables are plugged into the electronic equipment contained in the chassis. Often a series of cables will be plugged into a single modularised network card and a series of cards may be layered within a chassis. The modularised network cards are connected by a backplane. Typically a backplane is a printed circuit board which contains slots or sockets into which modularised cards, other electronic circuit boards and/or cables can be plugged. Typically, backplanes have front and rear sides and provide a physical connection between an interface processor or modularised card, the data signals and power distribution buses, all housed within the chassis.
The cabling issues associated with such densely laid out equipment can provide many challenges. The cables should be easy to replace and readily accessible whilst not being pulled across other pieces of equipment as this can limit accessibility. The cables should also be as short as possible to reduce cost and increase performance. Both electrical and optical fibre cables are restricted in how far they can be bent since this can cause stress, loss, and fatigue in the cable which may eventually,lead to down time of the network. It can often therefore be desirable to connect cables only to the rear of cards contained within a chassis in order to improve the maintainability.
Compact Peripheral Component Interconnect (cPCI) is an adaptation of the Peripheral Component Interconnect (PCI) which is an international standard specification for industrial computer applications. cPCI is often used for small, high-speed industrial computing applications where transfers occur between a number of high-speed cards. cPCI provides a way for rear cabling through the use of Rear Transition Modules (RTMs). Typically the RTM provides a connector to terminate an external cable and interface devices, recover the signal and convert it to digital format. In known modularised processing cards, an interface between an incoming signal and a hardware processor and filter is required, this is known as the interface circuit. The signal may then be converted into a digital format by the hardware processor before being transmitted to a host processor on a front card for further processing.
Typically an RTM connects to a Front processor card through a J3 or J5 connector. J3 and J5 connectors are standard connectors known in the art. However the use of these connectors is not mandated by Compact PCI and can be specific to the design of a processor card and RTM. Therefore, known RTMs can have limited functionality since they may only be compatible with one type of processor card. It is often however, desirable to have compatibility with any kind of commercially available front processor card. Since no pins are defined for power and ground in J3 and J5 connectors, known RTMs must derive power from the front processor card, but the pins used for power and ground are custom.
Another means for facilitating rear cabling can be provided by a PCI mezzanine card (PMC) which connects to a PMC site located on the front processor card. A PMC is a board that can be plugged into a standard interface on the front processor card. The hardware processing can be performed on the PMC but an RTM may still only be compatible with its mating PMC card. Both PMC and known RTMs do not necessarily support “hot-swap” technology.
An alternative to the use of RTMs with a standard PMC card is the use of a PMC card which contains the interface circuit. The external interface to the PMC card is through the front of the card cage and whilst no RTM is required, other problems may arise with this connectivity from the use of PMC cards. For example the orientation of PMC cards, i.e. connected into a slot on the front processor card and being parallel with the card can be unfavourable to the thermal behaviour of the module since the PMC card dissipates heat and can block the air flow in the chassis which may lead to the processor overheating. Furthermore, the external connection is to the front of the card cage and often it is desirable to connect to the rear of the card cage.